Induction motor



Dec. 29 1925 K. DAVIS INDUCTION MOQTOR Filed Nov. 22, 1920 3 Sheets-Sheet 1 K. DAVIS INDUCTION MOTOR Dec. 29 1925" Filed Nov. 22, 1920 5 Sheets-Sheet 2 ni/il/iiwnwlwi/l K. DAVIS INDUCTION MOTOR Dec. 29 I 3 Sheets-Sheet 5 Filed Nov. 22, 1920 BY I AT TOR NEY.

Patented Dec. I

e p I U TATES PATENT OFFICE.

xnmrrr nuns, on em. Bans-Dior, rnimsizrvwm, as sre'non. ro' mailmanrm'r rmnor new roan, my.

mnuorroi'r moron.

I Application fled member 2a, 1920., Serial 116.4%,841. j

To all whom it may concem:

lie it known that I KENNETH DAVIS, a citizen of the United tates, residing at St. Benedict, in the county of Gambrla and State of Pennsylvania, have made certain new and useful Improvements in induction Motors, of which the following is a specification. Y

The invention relates to induction motors,

and more es ecially to such motors which are self starting andhave a constant or continuous torque. Z

The present invention is directed to novel and useful improvements in induction motors, and in certain features thereof. is directed more especially to provide such a motor which is self-starting, is of. simpleconstruction as well as possessing other:

advantages. I

The invention consists in the novel parts, constructions, arrangements, combinations and improvements herein shown and described. v

The accompanying drawings, which are somewhat diagrammatic in character, illustrate an embodiment of the invention, in two somewhat difierent forms, and together with the description they serve to illustrate the I the stator field of Figsql and 2;

Fig. 5 is a section of a motor having a "discrotor taken on theline 5-5 of Fig. 6;

Fig. 6 is a section taken on lines 66 0.1:

Fig. 5'; s

ig. 7 is a section taken on line 7- -7 of Fig. 6; and

- Fig. 8 is a diagrammatic development of the stator field and -of the rotor shown in' Figs. 5, 6 and 7.

ig. 9 is a diagrammatic sectional elevation of a motor such as is shown. in Figs. 1 to 5, and indicating the resultant of the action of the eddy currents in theftorque plates; and

Fig. 10 is g the invention taken on line 1--1- a diagrammaticdevelo ment of a part ..o ij.;-Fig.-9 and indicating t e action the field by the torque plates.

T "of the eddy currents and the modification of e The invention as embodied in an exemlarymanner in the accompanying drawmgs, 1s'applied to a single phase induction motor which is self starting and which has a constant or continuous torque, and in Figs. 1 to 4 a form of motor is shown having'an external stator field and a drum rotor mounted on a central shaft. In Figs. 5 to 8 a form of motor is shown havin adi sc rotor mounted on the shaft with t e field arranged on both sides thereof.

The invention provides means for annulling or neutralizing the repelling action of the field upon the -armature or rotor windmgs or clrcuits' entering the-field, and substituting therefor an accelerating or propulslve force in the direction of rotation of the rotor. In accordance with ,one feature of the invention, in efi'ecting this, means are provided for creating countervailing eddy currents inthe gap between the stator and rotor neutralizing that portion of the field which otherwise would resist the entrance of the rotor windings into the field, which currents also exert apropulsive force upon the rotor in the direction of its rotation.

More m detail and as embodied, means, such as a metal plate, are inserted in the field in the gap between the stator and rotor there being set up in the plate countervailing eddy currents, which neutralize the repellin action of the field upon the rotor, and w ch also exert a positive attraction or rotative force in the direction of rot tion of the rotor, whereby the stator'field i caused to exert a continuous uni-directional torque upon the rotor, and whereby the motor is also rendered self-starting. That is, by the invention not only isthe repelling action of the first half 'of the field neutralized, but the rotor windings as they enter the field are drawn thereinto. 1

'Referring 'now in detail to the present exemplary embodiment as, illustrated in Figs. 1 to 4,, a frame or casing I is shown of general cylindrical form and havin end plates 2"and 3, which may have, suitable ventilating openings iand be otherwise formed to meet all-practical requirements In the'embodiment of said 'figures, a. stationary field is shown comprising pole pieces .6, 7, 8 and 9', with .gaps 10, 11, 12.-and 13, interposed therebetween, respectively.' The lelly spaced apart copper rods or bars 19,

preferably provided with covering strips of insulating material. connected together at their ends by annular plates 21 and 22 of copper or other conducting metal, that is, this may constitute essentially, what is usually known as a squirrel cage winding, all the bars being electrioally connected together at both ends by the I rings or other suitable connections.

The embodied form of means for neutralizin the repulsion or resistance of the field to the entry thereinto of the rotor circuits and for additionally exerting a propulsive force on the rotor in the direction of its rotation, comprises arcuate plates 25 and 26, interposed in the gap between. the magnets and the rotor, the plates being preferably of aluminum or other non-magnetic metal.

The plates I 'call for convenience torque lates.

Each of the plates is preferably of greater area than one of the poles of the field magnets and covers the entire pole in the sense that it is interposed between the entire face of the pole and the rotor. The plate 25 or 26 also preferably extends from the so covered pole towards and into close proximity to the next adjacent pole ofthe same or of opposite sign. In Figs. land 4 the plates 25 and 26 are shown extend ng past the respective covered poles and are each pravided with a turned up. or bent edge 27 extending intothe gap between the two adjacent oles, such turned up edges constituting a s ield. between the two poles.

In Figs. 5 to 8 the motor is shown with a rotor of disc form and with the remaining parts adapted to this type of machine The casing is shown of-general cylindrical form with a shell 30 and end plates 31 and 32, and

may have ventilating openings and be other.- wise adapted for practical conditions.

The field magnets 33 and 34 as shown 'are of arcuate form and are mounted in; pairs upon each of the end plates 31 and'32, re-

spectively, and each magnet has pole pieces 35 and 36, respectively. The. rotor is adisc 39 having radially disposed slots 40 formed therein, thereby dividing the disc int-o radially disposed bars 41 in the regionof the field. Disc 39 hasits hub 42 keyed on shaft 43, which shaft is journaled in the end plates 31 and 32.

The bars 19 are The means for neutralizing the repulsien or resistance of the field to the entrance thereinto of the successive bars 41 of the ';rotor, and for exerting upon the rotor an additional rotative force in the direction of its rotation, as already described, comprises arcuate plates 46 and '47, preferably but not necessarily of non-magnetic'n'1etal, such as aluminum, which are in pairs oh either side of the disc rotor 39. The plates 46 and 47 are of fiat'and arcuate form and are preferably of sui'iicient area to cover the cone sponding pole pieces in the sense already mentioned of being interposed between the entire area of the particular pole face and the disc rotor 39. i

,The plates 46 and 47 are also preferably of greater area than the pole face and ex-v tend into close proximity to the next adjacent pole of the same or opposite sign and preferably have a bent or turned up portion extending into the gap between the poles and closely adjacent to said pole, these bent up edges acting as 'a shield between the poles. The shield or plate placed over or covering a pole face as described serves to deflect the lines of force of the field and there are eddy currents thereby created or set up in the shield or plate. These eddy currents are opposite in direction to the portion of the field which resists the entrance of the non-current carrying circuit elements or coils of the rotor, and thus they neutralize or overcome the resistance to the rotation of the rotor in the desired direction. As already stated also, the eddy currents act to impose on the rotor a rotative force in the direction of its rotation. Thus the rotor is sub ected to a continuous torque in the desired direction and likewise is self-starting. The area and thickness of the torque plates affect their action, and as at present advised, I prefer to construct them of as great thickness as is found practicable consistent with a gap of greatest of efiiciency between the pole pieces and the rotor. This I have found in practice increases the torque. The same, result also is effected by likewise making the torque lates of relatively large area, that is, y having the plates of somewhat greater width than the covered pole piece and also having them extend lengthwise beyond the oles and'i'nto close proximity to the next a. j acen't pole on one side of the plate. j

Figs. 9 and 10 are also diagrammatic and are intended to illustrate the action'of the eddy currents in the torque plates, the rota-, tive effect of the eddy, currents being indi-. cated by the arrows 50. The plates a'ct also to diffuse or to weaken the field where the repellant action upon the rotor would be exerted, as indicated by the arrows 51.

The torque effecting action of the plates cangjbei controlled' or modified by moving themwith relation to their respective oles- In FigsL-Q and 7 an insulated bolt an nut adjustment-"52 is shown for thispu-rpose.

By this means the plates can be artially withdrawn from over thefaces o the respective pole"pieces or moved in the opposite dlrection, as desired, thereby decreasing or increasing the torque efiecting action of the p ate.

By .the invention, induction motor-is provided, which may be ,either single phase or polyphafs e, having all the desirable characteristics of a direct cur-- rent motor, buti-fgwhich will not run beyond a predeterminedihigh speed which isdetermined or fixed the design of the motor. Such a motor wi start under load, and will slow down and pick up speed with variations in the load, While maintaining a continuous torque. The motor has many applications, and one of its special adaptations is vfor locomotive and other traction work,

3knowledge, H r

periment, but I-do not wish the invention to v such as mine locomotives under current supplying conditions which are most practical" and economical in connection) with mine 'work." I w The statementot-the theory or principle of operation is correct to the best of my present gained by observation and "exaffected thereby.

be unnecessarily or harmfully limitedfor The'invention 1n broadest aspect is not limitedto the specific mechanisms shown and'described but departures may be made therefrom within the scope of the accom-. panyin claims without departing from the princip es of the invention and without sacrificing its chief advantages.

What I claim is 1.. An induction motor including in combination an inducing member with definite 7 proximity to the next adjacent;

oles, a rotor-having inducedcurrent carrying circuits, and a metal plate-interposed In the gap between a pole piece and the rotor and covering the entire pole piece.

2'. An induction motor including in com "bination an inducing memben with definitef poles, a rotor having induced current carry;- ing circuits, and a metal plate interposed ,inthegap between :a pole. piece .and the,- rotor and covering the entire pole piece; and extending ibeyondjthe'p-ole and into ole piece; 3. An induction motor'inclu in in com bination an inducing member wit definite poles, a rotorfhaving induced current carrying circuits, and a non-magnetic metal plate interposed in the gap between a'pole piece.

. and the rotor and covering theentirefpolepiece, the plate being at least equal-in. area to the pole iece.

4. An 1n uction motoriii'cluding in combination an inducing member with definite interposed in th and the rotor 1a an alternatinm current" 'for regulating poles, a rotor having induced current carrying circuits, and a metal plate interposed, in the gap between'a pole piece and the rotor andcovering the entire pole piece, and also extending between said pole piece and an adjacent pole piece of opposite sign.

6. An induction motor including in combination an inducing memberwith, definite oles, a rotor having induced current carrymg circuits and a metal plate interposed in the'gap between a pole piece and the rotor and covering the entire pole piece, and extending beyond the pole and into proximity a rotor having induced. current carryk tofthe next adjacent pole piece. and also extending between said pole piece and an adjacent pole piece.

7 An induction'motor including in combination an inducing member with definite I oles, a rotor having induced current carrying circuits and a non-magnetic metal plate illtBIPOSGdlII the ,gap between a pole piece and the rotor and covering the entire pole piece, and also extendin between said pole piece and an adjacent 'po e piece.

bination an inducingmember wit definite poles, a rotor having induced. current carrying circuits, and anon-magnetic metal plate interposed in the: gap between a pole piece and the rotor and covering the entire pole piece, and extendingbeyond the pole and 8. An induction motor includin in com-' into proximity to the next adjacent pole piece, and also extending between said pole piece and an adjacent pole piece.

- 9. An induction motor includin in com biilation aninducing member wit definite poles, arotor having induced current carry.- ing circuits, and "a metal' plate interposed in the gap between a pole iece and the rotor and coverin the entirepo e piece, and means the" relative position of the plate and pole piece.

10. An 'nd tion motor including. in combination an inducing member with'definite poles,-a rotor having-induced current ca'rrying circuits, and a metal plate interposed in the gap between a pole piece and therotort and covering the entire pole piece, and extending beyondthe pole and into proximity to the next adjacent ole piece, and means for regulating there ative position of the plate and pole piece. 4

Y .11. A 1nductionvmotorincluding'in com.-. :7

bination an inducing member with definite oles, a rotor having-induced current carry- 1 ing circuits, and a'metal plate interposed n the gap between a pole piece and the rotor and covering the entire pole piece, and means for movingthe plate transversely relatively to the pole piece.

12. An induction motor including in oombination an inducing member with definite poles, a rotor having induced current carrying circuits, and a metal plate interposed in the gap between a pole piece and the rotor and covering the entire pole piece, and ex- 10 tending beyond the pole and into proximity to the next adjacent'po'le piece, and means for moving the plate transversely relatively to the pole piece.

In testimony whereof, I have signed my 15 name to this specification.

I KENNETH DAVIS. 

